Ink jet printing mechanisms use pens that shoot droplets of ink onto a printable surface to generate an image. Ink jet printing mechanisms may be used in a wide variety of applications, including computer printers, plotters, copiers, and facsimile machines. For convenience, the concepts of the invention are discussed in the context of a printer.
An ink jet printer typically includes a print head having a multitude of independently addressable firing units. Each firing unit includes an ink chamber connected to a common ink source, and to an ink jet print nozzle. A transducer within each ink chamber provides the impetus for expelling ink droplets through the associated ink jet print nozzle. Typically, the transducer is a firing resistor which heats the ink until the ink droplets are expelled through the ink jet print nozzle.
Generally, a substrate supports the firing resistors. An orifice layer which includes the ink jet nozzles is attached to the substrate so that each ink jet nozzle corresponds with an associated firing resistor and forms an ink chamber.
To obtain a high resolution printed output, it is desirable to maximize the density of the firing units, requiring miniaturization of the print head components. The substrate that supports the firing resistors and the orifice layer that provides the ink jet nozzle above each resistor are subject to small dimensional variations that can accumulate and limit miniaturization.
Monolithic print heads have been developed through print head manufacturing processes which use photo imaging techniques similar to those used in semiconductor manufacturing. The components are constructed on a flat wafer by selectively adding and subtracting layers of various materials. Using photo-imaging techniques, dimensional variations are limited. Further variations do not accumulate because each layer is registered to an original reference on the wafer.
Existing monolithic print heads are complex to manufacture. Further, the ink jet nozzles are formed from either a polymer or metal material. Polymer and metal materials offer limited performance because the surfaces of these materials can be rough, and because these materials react corrosively with the ink. It is important that the surface of the ink jet nozzle be smooth so as to not interrupt the flow of ink through the ink jet nozzles. Further, corrosive reactions to the ink cause the ink jet nozzles to break down and deteriorate.
It is desirable to have an ink jet nozzle in which the surface of the ink jet nozzle is formed from a material which is smoother than presently existing materials. Further, the material would not react to ink which flows through the ink jet nozzle thereby increasing the useful life of the ink jet nozzle.